The present invention relates to an apparatus for removing ghost components which intermix into a received picture signal.
A picture signal includes a reference signal having GCR (Ghost Canceling Reference) signals which are extracted therefrom for removing the ghost components at a receiver side.
The GCR signals are usually rectangular pulse signals, that is, bar signals obtained by canceling a horizontal synchronizing signal and color burst signal as shown in FIGS. 1(a) and 1(b).
When extracting the GCR signals from the picture signal, the color burst signal may remain in the GCR signal, as shown in FIG. 1(c), as a component Ba, due to jitter included in the received picture signal, disturbance of the picture signal by such as scene change at TV broadcasting station side, disturbance of clock signals in the apparatus due to impulse noise and ghost, and the like.
In a conventional apparatus, the GCR signal shown in FIG. 1(c) is applied to a bandpass filter which allows a color subcarrier component of around 3.58 MHz to pass through for reducing the effect of a preceding ghost component. The bar signal is judged as to whether the remaining component Ba can be regarded as canceled while a first reference timing signal has a low level as shown in FIG. 1(d). The bar signal is further judged as to whether it has a level of a correct GCR signal while a second reference timing signal has a low level as shown in FIG. 1(e). If both judgements are positive, the bar signal is judged to be the correct GCR signal.
The conventional apparatus, however, sometimes misjudges that a bar signal out of a right timing is the correct GCR signal. For example, the bar signal shown in FIG. 1(f), which is out of a right timing compared with the GCR signal shown in FIG. 1(a), is judged to be correct because there is no color burst signal and the level of the bar signal is correct during the law level of FIG. 1(e).